As a lead-acid battery used in a vehicle or the like, there has been known a lead-acid battery disclosed in JP 2010-272264 A, for example. The lead-acid battery is configured such that, to suppress rising of an internal pressure of the battery, a gas generated in a container is discharged upward through an exhaust sleeve.
When a solution level of an electrolyte solution in the container rises and eventually reaches to a position of the exhaust sleeve, in the container, a pressure difference is generated between the inside of the exhaust sleeve communicating with an exhaust space and the outside of the exhaust sleeve. When the pressure difference is generated between the inside and the outside of the exhaust sleeve, a solution level of the electrolyte solution in the exhaust sleeve rises as the solution level in the container rises and hence, an electrolyte solution is liable to be leaked from an outlet of the exhaust sleeve. Accordingly, there has been studied a lead-acid battery having the configuration where a slit-like communication hole extending downward from a lower surface of a middle lid is formed in a wall portion which forms an exhaust sleeve. According to this configuration, a gas and an electrolyte solution are allowed to flow between the inside and the outside of the exhaust sleeve through the communication hole thus suppressing rising of a solution level of an electrolyte solution in the exhaust sleeve.